Catalytic Convertor problems of the 2001 Ford Windstar

My van started to have sounds of a flock of birds in the engine compartment. It stalled after running 20 miles, the engine light was the only light on. It was towed to the dealer. After running a diagnostic, I was told it was the cam sensor. They fixed that and off I went. Just to get down the road another 20 miles and my engine light came on once again. Back to the dealer I went the very next morning. The service guy I spoke with said" I do not know why that came on, but we will do a diagnostic on it again and find out. By this time I was pissed off. The mechanic said it was putting out codes p0141 and a p0147? ( anyway it was bank1 and bank2) running lean. I asked him when it was in yesterday, did you not notice the codes and he stated "I will have to pull it up on the hard copy, but he did not do it. Now another dealer at a different location has it today(2-13-07) diagnostics are almost the same but with added fuel injector problems. This is not the first time the engine light has came on. More like the 3rd time, with the same diagnostic codes. And each time I had to have almost the same thing done to it( like the injectors being flushed out 2x, now for the 3 rd time in 2 years). But each time the engine light came on, it was always the same codes. Obviously there is a problem with the engine components.